Method for spinal fusion

ABSTRACT

A system for fusing together opposing vertebra of a spine that defines a disc space therebetween. The system comprises a disc preparation instrument and an inserter assembly for use in the interbody fusion procedure. Disc preparation instrument comprises an elongate handle supporting a trial device at one end thereof. Inserter assembly comprises an elongate inserter supporting at one end thereof an interbody cage implant for insertion into the disc space. Disc preparation instrument provides a scoring element that scribes vertebral endplates at an appropriate scored location for anchor blades on the cage implant to engage the vertebral bodies. Inserter is used to introduce cage implant with anchor blades into the disc space to an appropriate depth so that the blades will be precisely positioned at the scored location created by the scoring element for penetration into the vertebral endplates.

CROSS-REFERENCE TO RELATED APPLICATION

This is a divisional application of U.S. application Ser. No.15/454,287, filed Mar. 9, 2017, now U.S. Pat. No. 9,937,055, whichclaims the benefit of U.S. Provisional Patent Application No.62/426,899, filed Nov. 28, 2016, the entire contents of which areincorporated by reference herein.

FIELD OF THE INVENTION

The subject invention relates to the field of spinal fusion, and moreparticularly, to delivery systems for, and methods of, delivering andimplanting spinal implants in a spinal column in the treatment of aspinal condition, including spinal fusion.

BACKGROUND OF THE INVENTION

Spinal implants such as interbody fusion devices are used to treatdegenerative disc disease and other damages or defects in the spinaldisc between adjacent vertebrae. The disc may be herniated or sufferingfrom a variety of degenerative conditions, such that the anatomicalfunction of the spinal disc is disrupted. Most prevalent surgicaltreatment for these conditions is to fuse the two vertebrae surroundingthe affected disc. In most cases, the entire disc will be removed,except for a portion of the annulus, by way of a discectomy procedure. Aspinal fusion device is then introduced into the intradiscal space andsuitable bone graft or bone substitute material is placed substantiallyin and/or adjacent the device in order to promote fusion between twoadjacent vertebrae.

One embodiment of a spinal fusion device is described in U.S. PatentPublication No. 2015/0202051, entitled “Spinal Fusion System”, filed onJan. 16, 2015 by Shigeru Tanaka et al. (the '051 Application) andassigned to the same assignee as the subject application. The spinalfusion system described in the '051 Application includes an interbodyfusion cage, a fixation plate, and an implanter. The fixation plate isreceivable in an open volume of the interbody fusion cage and includes asuperior blade and an inferior blade. The fixation plate is displaceablebetween a non-deployed state and a deployed state, wherein, when thefixation plate is received in the open volume and the fixation plate isin the non-deployed state, the superior and inferior blades extendgenerally parallel to each other. When the fixation plate is in thedeployed state, the superior and inferior blades extend oppositely fromeach other into the endplates of opposing vertebral bodies. In aparticular arrangement, the system may further include a trial/sizertool including a set of trial/sizer instruments. Such instruments mayincorporate a pre-scoring blade to break the vertebral endplate prior toinsertion of the spinal implant into the disc space and deployment ofthe blades into the endplates. Thus, a trial device may serve twopurposes, namely to test a size for a potential interbody fusion cageimplant and to prepare one or more vertebral endplate surfaces forreceiving the implant. The entire contents of the '051 Application areincorporated herein by reference.

While a trial device with a pre-scoring blade is beneficial, a systemhaving the capability of precisely correlating the entry location of ananchor blade into the vertebral endplate of one or more vertebral bodieswith the pre-scored location of such endplates is desirable.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an improved system forfusing together a superior vertebra and an inferior vertebra. The systemincludes a disc preparation instrument that provides both a trialingfunction to aid in selection of an appropriate size implant for theintended spinal disc space and an endplate scoring function that scribesthe vertebral endplates at an appropriate anterior-posterior positionfor the anchor plates of the spinal implant to engage the vertebralbodies. The instrument in one arrangement includes a trial device on oneend that approximates the size and shape of the cage implant, a depthstop element to limit over-insertion into the disc space, and a rotatingrasp element to slot the surfaces of the vertebral endplates on thesuperior and inferior faces at a controlled distance from the depthstop. The relative distance between the proximal face of the implanttrial and the depth stop is adjustable in order to countersink theimplant trial to a preferred depth with readable values (0, 1, 2, etc.).The scoring element is positioned within the implant trial at a locationsuitable for creating slots in the vertebral endplates that correspondto entry locations for blades on an anchor plate to penetrate thevertebral endplates. The scoring element is actuated rotationally aboutthe long axis of the instrument by a turning a handle at the oppositeend of the device in an oscillating fashion.

An implant inserter is used to introduce the interbody fusion cageimplant with an anchor plate into the disc space to an appropriate depthso that blades on the anchor plate will be deployed into the slotscreated by the scoring element of the implant trial. The adjustabledepth stop also includes readable values (0, 1, 2, etc.) that correspondto the depth settings on the implant trial. Intended use requires thatthe depth setting on the inserter matches the depth setting on theimplant trial in order to position the implant at the appropriate depth.With a pull rod, the implant inserter also provides a mechanism todeploy the anchor plate.

DESCRIPTION OF THE FIGURES

FIG. 1 is a top perspective view of a system, in accordance with oneembodiment of the present invention, comprising a disc preparationinstrument and an inserter assembly for fusing together opposingvertebra of a spine.

FIG. 2 is an exploded top perspective view of an interbody fusion cageimplant for use in the system of FIG. 1, comprising an interbody fusioncage and an anchor plate.

FIG. 3 is a top perspective view of the assembled cage implant of FIG. 2with the anchor plate being disposed in a first non-deployed position.

FIG. 4 is a side elevational view of the cage implant of FIG. 3 with theanchor plate being in the first non-deployed position.

FIG. 5 is a top perspective view of the assembled cage implant of FIG. 2with the anchor plate being disposed in a second deployed position.

FIG. 6 is a side elevational view of the cage implant of FIG. 5 with theanchor plate being in the second deployed position.

FIG. 7 is a top perspective exploded view of the disc preparationinstrument of the system shown in FIG. 1.

FIG. 8 is a perspective partially sectioned longitudinal view of thedisc preparation instrument of FIG. 7.

FIG. 9 is a side elevational view of the distal ends of the discpreparation instrument and the inserter assembly of the system of FIG. 1showing the spacing between the vertebral endplate scoring element andthe adjustable depth stop of the disc preparation instrument and thecorresponding spacing between the anchor plate penetration tips of thecage implant and the adjustable shoulder of the inserter assembly.

FIG. 10 is an enlarged partial view of the sectional view of the discpreparation instrument of FIG. 8 illustrating details of a depthindicator device.

FIG. 11 is a partial side elevational view of the distal end discpreparation instrument showing an example of a reading on the depthindicator device of FIG. 10 as it relates to the spacing between theproximal surface on the trial device and adjustable depth stop of thedisc preparation instrument.

FIG. 12 is a top perspective exploded view of the inserter assembly ofthe system shown in FIG. 1.

FIG. 13 is a perspective longitudinally sectioned view of the inserterassembly of FIG. 12.

FIG. 14 is a perspective view showing the distal end of the discpreparation instrument with the trial device being disposed in anintradiscal space between two opposing vertebral bodies of a spine, thevertebral bodies being partially sectioned for clarity, the scoringelement of the trial device being shown in a second position forming ascored location in the endplates of the vertebral bodies.

FIG. 15 is a perspective view showing the partially sectioned vertebralbodies of FIG. 14 and the distal end of the inserter assembly with thecage implant positioned in the intradiscal space and the penetrationtips of the anchor plate being in a first non-deployed position inalignment with the scored location formed in the vertebral endplates.

FIG. 16 is a perspective view showing the partially sectioned vertebralbodies of FIG. 14 and the distal end of the inserter assembly with thecage implant positioned in the intradiscal space and the penetrationtips of the anchor plate being in a second deployed position penetratingthe vertebral bodies through the scored location formed in the vertebralendplates.

FIG. 17 is a top perspective view of the cage implant of FIG. 5 with theanchor plate in a second deployed position and including a cap thereonfor bone graft retention.

DESCRIPTION OF THE EMBODIMENTS

For the purposes of promoting and understanding of the principles of theinvention, reference will now be made to the embodiments illustrated inthe drawings and described in the following written specification. It isunderstood that no limitation to the scope of the invention is therebyintended. It is further understood that the present invention includesany alterations and modifications to the illustrated embodiments andincludes further applications of the principles of the invention aswould normally occur to one skilled in the art to which this inventionpertains.

Referring now to FIG. 1, a system 10 is shown for fusing togetheropposing vertebra of a spine that defines a disc space therebetween.System 10 comprises a disc preparation instrument 100 and an inserterassembly 200 for use in the interbody fusion procedure. Disc preparationinstrument 100 comprises an elongate handle 102 supporting a trialdevice 104 at one end thereof. Inserter assembly 200 comprises anelongate inserter 202 supporting at one end thereof an interbody cageimplant 204 for insertion into the disc space. Disc preparationinstrument 100 provides a scoring element that scribes vertebralendplates at an appropriate anterior-posterior location for anchorblades on the cage implant to engage the vertebral bodies. Inserter 202is used to introduce cage implant 204 with anchor blades into the discspace to an appropriate depth so that the blades will be deployed intoslots created by the scoring element of implant trial 104, as will bedescribed.

Turning now to FIGS. 2-6, details of interbody cage implant 204 arefirst described. Cage implant 204 as shown in FIG. 2 comprises a cage206 and anchor plate 208. Cage 206 is formed of size and configurationfor insertion into the disc space between opposing vertebral bodies.Cage 206 comprises a pair of spaced opposing side walls 210 and 212 anda rear wall 214 therebetween. Side walls 210, 212 and the rear wall 214formed a generally U-shaped open cavity 216 for receipt of anchor plate208 and bone graft. An exterior surface 214 a of rear wall 214 defines adistal surface of cage 206 while the exterior surfaces at the free ends210 a and 212 a of sidewalls 210 and 212 define a proximal surface atthe opposite end of cage 206. Cage 206 includes a top surface 218 and abottom surface 220. Top surface 218 and bottom surface 220 may be formedto each include respective anti-expulsion features 218 a, 220 a, such asteeth, ratchetings or other suitably abrasive surfaces. In onearrangement, top surface 218 and bottom surface 220 may be formed totaper downwardly toward distal surface 214 a defining cage 206 to have alordotic configuration as well as to facilitate entry of cage 206 intothe disc space. Each side wall 210 and 212 has a respective slot 222 and224 extending at an angle through top surface 218. Each side wall 210and 212 further includes a respective slot 226 and 228 extending at anangle through bottom surface 220. Each of top slots 222, 224 and bottomslots 226, 228 communicates with open cavity 216. Sidewall 210 includesan opening 230 extending therethrough and a channel 232 extending intointerior surface 210 b of sidewall 210. Sidewall 212 includes an opening234 extending therethrough and a channel 236 extending into an interiorsurface of sidewall 212. Openings 230, 234 and channels 232, 236facilitate the releasable connection of inserter 102 thereto, as will bedescribed. In one particular arrangement, cage 206 is formed ofpolyetheretherketone (PEEK), although cage 206 may be formed of othersuitable biocompatible materials, such as, e.g., titanium, stainlesssteel or carbon fiber PEEK.

Still referring to FIG. 2, anchor plate 208 comprises a base 238supporting an upper blade 240 and a lower blade 242. Base 238 has athreaded opening 238 a therethrough for threaded connection to inserter102, as will be described. Upper blade 240 is attached to base 238 by aplastically deformable joint 244 and lower blade 242 is attached to base238 by a plastically deformable joint 246. Upper blade 240 and lowerblade 242 have elastic, spring properties. Upper blade 240 includes apair of laterally spaced wings 240 a and lower blade 242 includes a pairof laterally spaced wings 242 a. Wings 240 a are sized and configured toextend into respective top slots 222 and 224 extending through topsurface 218 and wings 242 a are sized and configured to extend intorespective bottom slots 226 and 228 extending through bottom surface 220when the blades 240 and 242 are deployed, as will be described. Upperblade 240 includes a penetration tip 240 b at its distal free end andlower blade 242 includes a penetration tip 242 b at its distal free end.Penetration tips 240 b and 242 b are each formed to be sufficientlysharp to penetrate into the endplates of adjacent vertebral bodies. Eachrespective tip 240 b and 242 b may be provided with a notch 240 c and242 c to facilitate retention of each blade in a respective vertebralendplate. In one particular arrangement, anchor plate 208 is formed oftitanium, although anchor plate 208 may be formed of other suitablebiocompatible materials, such as, e.g., stainless steel.

FIGS. 3 and 4 show anchor plate 208 disposed in cage 206 in anon-deployed first position. In this stage, anchor plate 208 issupported by cage 206 and is disposed between distal surface 214 a andproximal surface 210 a, 212 a with base 238 being situated against orclosely adjacent to rear wall 214. Wings 240 a of upper blade 240 arespaced distally of and not extending into slots 222 and 224 of cage 206,as depicted in FIG. 3. Similarly wings 242 a of lower blade 242 arespaced distally of and not extending into slots 226 and 228 of cage 206.In this position, blade penetration tips 240 b and 242 b may extendslightly above and below respective top and bottom surfaces 218 and 220,as illustrated in FIG. 4. It should be appreciated, however, that suchblade penetration tips 240 b and 242 b may also lie substantially flushwith or within respective top and bottom surfaces 218 and bottom surface220. The location of the anchor blades 240, 242 in the non-deployedposition relative to the cage proximal surface 210 a, 212 a is used inconjunction with the disc preparation instrument 100, as will bedescribed, to create a scored location in the vertebral endplates thatcorresponds to entry locations for the penetration tips 240 b, 242 b ofthe anchor blades 240, 242 upon deployment. In this regard, penetrationtips 240 b, 242 b are spaced from cage proximal end 210 a, 212 a by apredetermined, set spacing, S₁ as shown in FIG. 4. It should beunderstood that other locations on cage implant 204, such as, forexample the spacing of top slots 222, 224 or bottom slots 226, 228 fromcage proximal surface 210 a. 212 a may also be used as referencelocations for correlation with the scoring function of the discpreparation instrument 100.

Upper blade 240 is deployed upon movement of anchor plate 208 in theproximal direction by inserter 202, as will be described. Upon suchproximal movement of anchor plate 208, upper blade 240 is caused byinserter 202 to deploy by moving arcuately in an upward direction suchthat wings 240 a extend into and are constrained by the surfacesdefining upper slots 222 and 224. During such movement of anchor plate208, lower blade 242 is caused to deploy by inserter 202 by movingarcuately in a downward direction such that wings 242 a extend into andare constrained by the surfaces defining lower slots 226 and 228. Thepositions of upper blade 240 and lower blade 242 in the second deployedposition are illustrated in FIGS. 5 and 6. Further details of an anchorplate with deployable anchor blades deployed by an implant inserter aredescribed in the '051 Application, incorporated herein by reference inits entirety.

Turning now to FIGS. 7-11, the details of disc preparation instrument100 are described. Disc preparation instrument 100 comprises elongatehandle 102 supporting a trial device 104, as noted hereinabove. Body 106has a distal surface 108, a proximal surface 110, a top surface 112 anda bottom surface 114. Top surface 112 has a top opening 112 a and bottomsurface 114 has a bottom opening (not shown) similar to top opening 112a. Body 106 supports a rotatably movable scoring element 116 disposedbetween distal surface 108 and proximal surface 110 and having a firstupper portion 116 a and a second lower portion 116 b. Scoring element116 is selectively movable from a first position wherein first portion116 a and second portion 116 b are both disposed interiorly of trialdevice 104 as shown in FIG. 8 to a second position shown in FIG. 9wherein first portion 116 a extends exteriorly of body 106 through topopening 112 a and second portion 116 b extends exteriorly of body 106through bottom opening. First portion 116 a and second portion 116 beach includes in a particular aspect a rasped scoring surface along theedges thereof to facilitate scoring of the surfaces of vertebralendplates, although other abrasive surfaces may also be used. Whilescoring element 116 in the arrangement shown is rotatable it should beappreciated that first portion 116 a and second portion 116 b may also,in an alternative approach, be supported to move linearly from the firstposition to the second position. Trial device 104 may be used for thedual purpose of scoring and trialing, but could be used only forscoring. In the dual configuration, trial body 106 is of size andconfiguration approximating the size and configuration of cage implant204 for insertion into the disc space. In this regard, trial body 106may be formed to taper downwardly toward distal surface 108 definingtrial body 106 to have a lordotic configuration, as illustrated in FIGS.7 and 8, in the same manner as cage implant 204.

With reference still to FIGS. 7-8, elongate handle 102 has a distal end102 a and a proximal end 102 b, trial device 104 being supported atdistal end 102 a. Handle 102 comprises a handle grip 120 including aninner sleeve 122 affixed thereto for joint movement. A lumen 124 extendsfully through handle grip 120 and inner sleeve 122. The distal end 122 aof inner sleeve 122 is suitably fixedly attached in one arrangement toan attachment ring 106 a provided at the proximal surface 110 of trialbody 106. It should be appreciated that trial body 106 may be releasablyattached to inner sleeve 122 such that a kit of differently sized trialbodies 106 may be provided in a kit for selective use with inner sleeve122. An elongate shaft 126 having a distal end 126 a and a proximal end126 b extends within lumen 124 of handle 102 through handle grip 120 andinner sleeve 122 and is rotatable but not translatable within lumen 124.Translation of shaft 126 relative to handle grip 120 is prevented bypins 127 disposed in a groove 129 extending around the circumference ofshaft 126. Distal end 126 a includes an engagement feature 126 c forextending into trial body 106 and engaging scoring element 116. In oneparticular arrangement, engagement feature 106 c is a multi-faceteddrive sized and configured to engage with a complementary sized andconfigured opening 116 c formed in scoring element 116. Shaft 126 has anactuator 128 at proximal end 126 b, actuator 128 being operable torotate shaft 126 and thereby scoring element 116 at the distal end 126 athereof. In one particular arrangement actuator 128 comprises arotatable T-handle 130 for rotating shaft 126 and scoring element 116.T-handle 130 may be oriented with respect to scoring element 116 in amanner to visually determine when scoring element 116 is in the firstposition or the second position, as described above. For example, whenT-handle 130 is oriented in a generally horizontal position scoringelement 116 may be in the first position whereby first portion 116 a andsecond portion 116 b are disposed interiorly of trial device 104. WhenT-handle 130 is oriented in a generally vertical position after havingbeen rotated approximately 90 degrees to the second position, firstportion 116 a of scoring element 116 extends exteriorly of body 106through top opening 112 a and second portion 116 b extends exteriorly ofbody 106 through bottom opening, as shown in FIG. 9.

The location of the scoring element 116 relative to the trial bodyproximal surface 110 is used in conjunction with the inserter assembly200, described hereinabove, to create a scored location in the vertebralendplates that corresponds to entry locations for the penetration tips240 b, 242 b of the anchor blades 240, 242 upon deployment. In thisregard, scoring element 116, in particular its distal surface 116 c, isspaced from trial body proximal end 110 by a predetermined, set spacing,S₂ as shown in FIG. 9. Spacing, S₂ is predetermined to be approximatelythe same dimension as spacing, S₁, namely, the spacing penetration tips240 b, 242 b of anchor blades 240, 242 are spaced from cage proximal end210 a, 212 a. As such, positioning the proximal surfaces of the trialbody 106 and cage implant at the same location in the disc space willalign the anchor blade penetration tips 240 b, 242 b with a scoredlocation formed in the endplates of opposing vertebral bodies by scoringelement first and second portions 116 a, 116 b. It should be understoodthat other locations on trial body 106, such as, for example theproximal surface 116 d of scoring element 116 may also be used as areference location for correlation with the anchor blade penetrationtips 240 b, 242 b.

Referring further to FIGS. 7-9 and also to FIG. 10, handle 102 furthercomprises an elongate outer sleeve 132 supported by inner sleeve 122which extends through a lumen 134 extending through outer sleeve 132.Outer sleeve 132 is coupled to inner sleeve 122 by a pin 136 through aslot 132 b as shown in FIG. 9 that allows translation of outer sleeve132 relative to inner sleeve 122, but not rotation. The extent ofrelative axial movement is controlled by the axial length of slot 132 b.Outer sleeve 132 supports an adjustably movable depth stop 138 at adistal end 132 a of outer sleeve 132. Depth stop 138 is sized andconfigured to engage an exterior surface of a vertebra when trial device104 is disposed in the intradiscal space, as will be described.

Handle 102 includes at the proximal end 132 c of outer sleeve 132 anadjustment knob 140 to axially move outer sleeve 132 and thereby depthstop 138 along inner sleeve 122. Outer sleeve 132 has at its proximalend 132 c an externally threaded extent 132 d. A collar 142 is disposedwithin adjustment knob 140, collar 142 having an opening 142 a withinternal threads 144. Internal threads 144 threadably engage externalthreads 132 d at the proximal end 132 c of outer sleeve 132. Adjustmentknob 140 is pinned to collar 142 by pins 146 that prevent rotation ofadjustment knob 140 relative to collar 142, but allow translation. Thus,when adjustment knob 140 is rotated in a clockwise motion when handlegrip 120 is held by a user, collar 142 will likewise be rotated causingaxial movement of outer sleeve 132 and depth stop 138 thereon in thedistal direction on inner sleeve 122 as result of the threaded couplingbetween external threads 132 d and internal threads 144.

In a particular arrangement a releasable lock 147 is provided betweenadjustment knob 140 and handle grip 120, as depicted in FIGS. 7 and 8,to prevent inadvertent axial movement of outer sleeve 132 relative toinner sleeve 122. In this arrangement, at the interface of handle grip120 and inner sleeve 122, a locking surface 148, such as a hex surface,is formed. An opening 140 a as shown in FIG. 10 having a complementaryhex engagement is formed on adjustment knob 140. A compression spring154 is captured between an interior surface 152 of adjustment knob 140and collar 142. A slot 156 is formed through adjustment knob 140 toreceive at least one pin 146, slot 156 allowing a limited amount ofaxial movement of pin 146 therewithin. In the normal state, spring 154applies a force against interior surface 152 of adjustment knob 140causing hex engagement surface 140 a to couple with hex locking surface148. In this state, relative rotation between adjustment knob 140 andinner sleeve 122 is prevented. Applying a manual force to adjustmentknob 140 in the distal direction to overcome the bias of spring 154 willcause limited distal movement of adjustment knob 140 as pin 146 axiallymoves within adjustment knob slot 156. Such limited axial movement issufficient to cause separation of adjustment knob 140 from lockingsurface 148, thereby permitting rotation of adjustment knob 140 andaxial movement of outer sleeve 132 and depth stop 138 relative to innersleeve 122. Release of such manual force allows adjustment knob 140 tospring back under the bias of spring 154 in the proximal direction toengage locking surface 148.

Turning now to FIGS. 10-11, handle 102 further comprises an indicatordevice 158 operable with the axial movement of outer sleeve 132 alonginner sleeve 122 to provide a visual indication of a plurality ofselectable distances that depth stop 138 may move relative to trialdevice 104, as will be described. In a particular arrangement, innersleeve 122 is provided with a plurality of markings 160 or othersuitable indicia, as shown in FIGS. 10 and 11. Such markings may be inthe form of stripes or bands formed around the circumference of innersleeve 122. Each marking 160 is representative of a different distancethat depth stop 138 is spaced from a location on the trial body 106.Such location on the trial body 106 may be its proximal surface 110.Each distance, D, for example, that the depth stop 138 is selectivelyspaced from the proximal surface 110 of trial body 106 is indicated by adifferent marking 160 that will be visually observable through one of anequal number of windows 162 formed through outer sleeve 132. Windows 162are axially spaced from each other along outer sleeve 132 atapproximately the same distances, with each window representing a changein distance, D of approximately 1 mm. Markings 160 are spaced from eachother along inner sleeve 122 at different distances that are ordered bytiming in dimensional increments, such as in increments of millimeters.As such, when outer sleeve 132 and depth stop 138 are axially movedrelative to inner sleeve 122 and hence trial body 106 affixed thereto,windows 162 will axially move relative to markings 160 and only onemarking 160 will appear through one window 162 at a time. Accordingly,in the arrangement shown in FIGS. 10 and 11, indictor device 158includes four windows, denoted a “0”, “1”, “2,” and “3”. The spacing inindicator device 158 from marking “0” to marking “1” is 1 mm greaterthan the spacing between windows 162. The spacing from marking “1” tomarking “2” is 2 mm greater than the spacing between windows 162. Thespacing from marking “2” to marking “3” is 3 mm greater than the spacingbetween windows 162. The “0” window may indicate a distance, D ofapproximately 2 mm, the “1” window a distance, D of approximately 3 mm,the “2” window a distance, D of approximately 4 mm, and the “3” window adistance, D of approximately 5 mm. As illustrated in FIG. 11, marking160 appears in window “2”, indicating that depth stop 138 is spaced adistance, D of approximately 4 mm from trial body proximal surface 110.

Turning now primarily to FIGS. 12 and 13, the details of elongateinserter 202 of inserter assembly 200 are described with the details ofcage implant 204 having been described above. Elongate inserter 202 hasa distal end 202 a and a proximal end 202 b, cage implant 204 beingsupported at distal end 202 a. Inserter 202 comprises an inserter grip250 including an inner shaft 252 affixed thereto. A lumen 254 extendsfully through inserter grip 250 and inner shaft 252. The distal end 252a of inner shaft 252 includes a cage implant support 256 suitablyaffixed to inner shaft 252 by a clip 258 or other suitable attachmentdevice. Implant support 256 includes a pair of axially extendinglaterally spaced insertion tips 260. Insertion tips 260 project axiallybeyond contact surface 262 and are sized and configured to enter opening216 of cage implant 204 with one tip 260 being situated between base 238of anchor plate 208 and one sidewall 210 and the other tip 260 betweenbase 238 and the other sidewall 212. Laterally outwardly of insertiontips 260 implant support 256 includes a pair of flexible hooks 264 atthe free end thereof. During insertion of tips 260 into cage implantopening 216, flexible hooks 264 will flex toward each other and ridewithin channels 232, 236 (FIG. 2) in respective sidewalls 210, 212 untilhooks 264 reach openings 230, 234 in sidewalls, at which point hooks 264snap back in a manner to releasably attach implant support and therebyinserter 202 to cage implant 204. Upon releasable attachment of hooks264 to cage implant 204, the distal ends 260 a of each tip 260 lieagainst or closely near the interior surface of rear wall 214 whilecontact surface 262 lies against or closely near proximal surface 210 a,212 a of cage implant 204 (See FIG. 9). Cage implant support 256 furtherincludes a pair of elongate slots 266 extending therethrough, thefunction of which will be described.

Proximal end 252 b of inner shaft 252 is affixed to inserter grip 250 bya pin 268 which prevents any relative rotation or translation betweeninner shaft 252 and inserter grip 250. Elongate inserter 202 includes adeployment knob 270 threadably supported at the proximal end of insertergrip 250. Deployment knob 270 includes external threads 270 a forthreaded engagement with internal threads 250 a interiorly of insertergrip 250, as shown in FIG. 13. Threads 270 a and 250 a are left-handedthreads, meaning that upon clockwise rotation of deployment knob 270relative to inserter grip 250, deployment knob will translate axially inthe proximal direction. Deployment knob 270 further includes a lumen 272extending therethrough in axial communication with lumen 254 extendingthrough inserter grip 250 and inner sleeve 252. Deployment knob 270 ispinned to inserter grip 250 by pins 274 that reside in a groove 276 indeployment knob 270, grove 276 allowing a limited amount of axialtranslation and preventing deployment knob 270 from being removed frominserter grip 250.

An elongate pull rod 278 extends through lumen 254 of inserter grip 250and inner sleeve 122 and through lumen 272 of deployment knob 270.Distal end 278 a of pull rod 278 includes threads 280 for releasablethreaded engagement with the threads of threaded opening 238 a in anchorplate 208. A pull rod knob 282 is fixedly attached to the proximal end278 b of pull rod 278. Pull rod 278 is attached to anchor plate 208 byinserting distal end 278 a through deployment knob lumen 272 and throughlumen 254 of inserter grip 250 and inner sleeve 252 until threads 280enter threaded opening 238 a of anchor plate 208. Pull rod knob 282 isrotated in a clockwise motion to thread pull rod threads 280 intothreaded anchor plate opening 238 a. Anchor plate 208 is moved to deployanchor blades 240 and 242 upon rotation of deployment knob 270 in aclockwise motion. Due to the left-handed threaded connection, deploymentknob 270 will move with clockwise rotation in the proximal directionuntil proximally facing surface 270 b on deployment knob 270 contactsdistally facing surface 282 a on pull rod knob 282. Clockwise rotationof deployment knob 270 will draw pull rod 278 in the proximal direction,deploying anchor blades 240 and 242 to the deployed second position asdescribed above and shown in FIG. 6. When pins 274 engage the distalside of groove 276 proximal motion of deployment knob 270 is completeand anchor blades 240 and 241 are fully deployed.

Elongate inserter 202 further incudes an inner sleeve 284 having a lumen286 extending fully theretrough and through which inner shaft 252 isreceived. The distal end 284 a of inner sleeve 284 is suitably fixedlyattached to a shoulder support 290 such that shoulder support 290 ismovable jointly with inner sleeve 284. Shoulder support 290 includes achannel 292 within which cage implant support 256 is slidably received.Shoulder support 290 has pair of pins 294 extending respectively througha pair of top openings 290 a and a pair of bottom openings 290 b. Pins294 also extend through slots 266 extending through cage implant support256. The elongated extent of slots 266 allow shoulder support 290 toslide axially in the proximal direction by a limited amount relative tocage implant support 256. During such proximal sliding movement, pins294 contact the flexible hooks 264 at the ends thereof causing hooks 264to compress medially laterally toward each other in a manner to movehooks 264 out from cage implant openings 230 and 234 so that cageimplant support 256 and thereby elongate inserter 202 may be separatedfrom cage implant 204 when a surgical procedure is complete.

The opposite proximal end 284 b of inner sleeve 284 is received though alumen 296 extending fully through an outer sleeve 298 slidably supportedon inner sleeve 284. Proximal end 284 b of inner sleeve 284 extends intoa lumen 302 extending fully through a depth controller 300, proximal end284 b being fixedly attached to depth controller 300 such that innersleeve 284 and depth controller 300 are movable jointly. Externalthreads 304 are provided about the outer circumference of depthcontroller 300. Proximal end 300 a of depth controller 300 has a reduceddiameter that is received through a lumen 306 extending fully through arotatable adjustment member 308. Lumen 306 includes internal threads 310extending circumferentially thereabout. Proximal end 300 a of controller300 extends into a lumen 312 of a hook actuator 314 having a lumen 312extending fully therethrough. Proximal end 300 a of depth controller 300is fixedly attached to hook actuator 314 such that inner sleeve 284,depth controller 300 and hook actuator 314 are all movable jointly.

Referring still to FIGS. 12 and 13, outer sleeve 298 has a distal end298 a and a proximal end 298 b. Distal end 298 a includes an axiallyextending arm 316 affixed thereto and terminating at its distal end in ashoulder 318. Shoulder 318 is axially movable relative to shouldersupport 290 and is sized and configured to engage an exterior surface ofa vertebra when cage implant 204 is disposed in the intradiscal space,as will be described. As such, shoulder 318 serves as an adjustabledepth stop for use in aligning blade penetration tips 240 b, 242 b ofcage implant 204 with a scored location formed on endplates of opposingvertebral bodies by scoring element 116 of disc preparation instrument100. Arm 316 is sized and configured to be slidably received in track290 b formed on an upper surface of shoulder support 290, as depicted inFIG. 12. Track 290 b is defined by a pair of laterally spaced rails 290c. Rails 290 c permit axial movement of arm in track 290 b, butsubstantially prevent rotational movement between inner sleeve 284 andouter sleeve 298.

Proximal end 298 b of outer sleeve 298 has a pair of axially spacedannular plates 320 defining a grove 322 therebetween, as shown in FIG.12. Outer sleeve 298 is attached to depth adjustment member 308 by apair of pins 324 extending through openings 308 a in adjustment member308 and residing in groove 322. As such, adjustment member 308 mayrotate relative to outer sleeve 298, but not translate relative thereto.In assembly as shown in FIG. 13, external threads 304 of depthcontroller 300 threadably engage internal threads 310 on adjustmentmember 308. Rotation of adjustment member 308 in a clockwise motion wheninserter grip 250 is held in a stationary position will cause outersleeve 298 and hence shoulder 318 affixed thereto to move axially in thedistal direction toward cage implant 204. Rotation of adjustment member308 in a counterclockwise motion will cause outer sleeve 298 andshoulder 318 to move axially in the proximal direction away from cageimplant 204.

As described hereinabove, shoulder support 290 is configured to slideaxially in the proximal direction by a limited amount relative to cageimplant support 256 in a manner to cause hooks 264 to compress and allowelongate inserter 202 to be separated from cage implant 204 uponcompletion of a surgical procedure. Such movement of shoulder support290 in the proximal direction is effected by movement of hook actuator314. As explained above, hook actuator 314 is fixedly attached to depthcontroller 300, which in turn is fixedly attached to inner sleeve 284,and which in turn is fixedly attached to shoulder support 290. Axialmovement of hook actuator 314 thus axially moves the entire subassemblyof hook actuator 314, depth controller 300, inner sleeve 284 andshoulder support 290 axially on inner shaft 252. Furthermore, asrotatable adjustment member 308 is threadably engaged with depthcontroller 300 and outer sleeve 298 is axially coupled to rotatableadjustment member 308, upon axial movement of hook actuator, in additionto axial movement of the subassembly, adjustment member 308 and outersleeve 298 with shoulder 318 thereon will also axially move with thesubassembly.

In order to prevent inadvertent movement particularly of shoulder 318relative to cage implant 204, a lock is provided. In this arrangement asshown in FIGS. 12 and 13, a lock 326 comprises a rotatable lock knob 328configured to selectively engage portions of hook actuator 314 in amanner to allow and prevent axial movement of the hook actuator, andhence inadvertent movement of shoulder 318. Lock knob 328 supports ahelical compression spring 330 at one end, the free end 330 a of spring330 being sized and configured to engage a proximally facing contactsurface 314 a on hook actuator 314. A pair of arcuate slots 328 a isformed into lock knob 328, slots 328 a in one arrangement beingapproximately diametrically opposed. Lock knob 328 is suitably supportedat the distal end 250 b of inserter grip 250 for rotational but nottranslational movement. Hook actuator 314 includes a pair ofcomplementary arcuate tabs 314 b projecting proximally therefrom, tabs314 b being sized and configured to enter knob slots 328 a. In normaluse, tabs 314 b contact lock knob 328 at the surfaces 328 b betweenslots 328 a thereby preventing axial movement of hook actuator 314. Uponrotation of lock knob 328, tabs 314 b may be aligned with knob slots 328a, allowing tabs 314 b to enter slots 328 a and thereby allow axialmovement of hook actuator 314 in the proximal direction. Such movementis achieved by manually compressing spring 330 an amount to allowshoulder support 290 to move proximally to cause pins 294 on implantsupport 256 to depress hooks 264 for removal of elongate inserter 202from cage implant 204. Upon release of the manual force on hook actuator314, hook actuator 314 will return to its original position under thenormal bias of spring 330 whereby lock knob 328 may be rotated toposition tabs 314 b between slots 328 a on surfaces 328 b to preventfurther axial movement.

With reference still to FIGS. 12 and 13, inserter 202 further comprisesan indicator device 332 substantially the same as indicator device 158on handle 102 of disc preparation device 100, described above. As such,indicator device 332 is operable with the axial movement of outer sleeve298 along inner sleeve 284 to provide a visual indication of a pluralityof selectable distances that shoulder 318 may move relative to cageimplant 204. In a particular arrangement, inner sleeve 284 is providedwith a plurality of markings 334 or other suitable indicia, as shown inFIG. 12. Such markings 334 may be in the form of stripes or bands formedaround inner sleeve 284. Each marking 334 is representative of adifferent distance that shoulder 318 is spaced from a location on thecage implant 204 and will be visually observable through one of an equalnumber of windows 336 formed through outer sleeve 298. Such location onthe cage implant 204 may be its proximal surface 210 a, 212 a. Withindicator device 332 being substantially the same as indictor device158, the distance, D that the depth stop 138 is spaced from the proximalsurface 110 of trial body 106, as determined by a reading on indicatordevice 158, may be transferred to indicator device 332 of inserterassembly 200. As such, transferred distance, D for inserter assembly 200would determine the spacing between shoulder 318 and proximal surface210 a, 212 a of cage implant 204, as shown in FIG. 9. For example, areading with a marking 160 appearing in window “2” of indicator device158 would be transferred to indicator device 332 by rotating adjustmentmember 308 to move outer member 298 relative to inner member 284 until amarking 334 appears in the “2” window. Thus, in the example providedabove, the distance, D between shoulder 318 and proximal surface 210 a,212 a of cage implant 204 would be approximately 4 mm, the same as thedistance between depth stop 138 and the proximal surface 110 of trialbody 106. Thus, the spacing, X₁ between anchor penetration tips 240 b,242 b and shoulder 318 of inserter assembly 200 is S₁+D and the spacing,X₂ between the scoring element 116 and the depth stop 138 of discpreparation instrument 100 is S₂+D. With S₁=S₂, then S₁+D=S₂+D andX₁=X₂. Accordingly, the precise location of the scored location formedby scoring element 116 can be ascertained for positioning andpenetration by anchor penetration tips 240 b, 242 b by transferring thedistance, D from the disc preparation instrument 100 to the inserterassembly 200.

Having described the system 10 comprising disc preparation instrument100 and inserter assembly 200, a method for use in an interbody fusionprocedure is described, with particular reference to FIGS. 14-16. In oneparticular approach, system 10 is used to fuse together a superiorvertebra 338 and an inferior vertebra 340 in the cervical region of thespine in a procedure known as a Smith-Robinson approach. It should beappreciated, however, that system 10 may also be used in interbodyfusion procedures in other regions of the spine. Superior vertebra 338includes an inferior endplate 338 a, a vertebral body 338 b, and anexterior anterior surface 338 c. Inferior vertebra 340 includes asuperior endplate 340 a, a vertebral body 340 b and an exterior anteriorsurface 340 c. Superior endplate 338 a and inferior endplate 340 adefine an intradiscal space 342 therebetween. Endplates 338 a, 340 aconsist primarily of relatively hard bony/cartilaginous material that isoften difficult to penetrate for fixing fusion implants for interbodyfusion purposes. In the cervical spine procedure, access to the spine isoften provided by forming an incision through the anterior portion ofthe patient's neck to expose superior and inferior vertebrae 338, 340.As such, exterior surfaces 338 c, 340 c of superior vertebra 338 andinferior vertebra 340, respectively, are anterior surfaces. A suitablediscectomy is performed to provide an appropriate disc space 342 forreceipt of cage implant 204. It should be understood that access may beprovided in other approaches, such as posterior or lateral dependingupon the nature of the procedure and the surgeon's preference.

Disc preparation instrument 100 is used to suitably prepare opposingvertebral endplates 338 a, 340 a for receipt of cage implant 204. Handle120 of disc preparation instrument 100 is used to introduce trial device104 into the disc space 342 using suitable imaging techniques, such asfluoroscopy. Such imaging includes a side view from the lateralperspective so that the depth of trial device 104 along theanterior-posterior (A/P) direction may be observed. Upon determinationof an appropriate depth of trial device 104 in the A/P direction,adjustment knob 142 is released from lock 147 by applying a manual forceto adjustment knob 140 in the distal direction to overcoming the bias ofspring 154. Adjustment knob 140 is rotated in a clockwise motion whileadjustment knob 140 is separated from lock 147 to move outer sleeve 132until depth stop 138 contacts exterior anterior surface 338 c ofsuperior vertebra 338. It should be understood that depth stop 138 inthe alternative may also be configured on disc preparation instrument100 to contact exterior anterior surface 340 c of inferior vertebra 340.The manual force on adjustment knob 140 is released thereby causingadjustment knob 140 to reengage with lock 147 to thereby fix theposition of adjustment stop 138 against anterior surface 338 c.Indicator device 158 is observed to determine through which window 162,such as the “2” window, a marking 160 appears, with such window 162being suitably noted. If marking 160 is not evident through any onewindow 162, the depth stop 138 of trial device 104 may be adjusted inthe A/P direction by rotating adjustment knob 140 until a marking 160appears through a particular window 162. This establishes the distance,D, as described hereinabove, that proximal surface 110 of trial device104 is spaced in disc space 342 from depth stop 138 and hence exterioranterior surface 338 c of vertebra 338. It further establishes spacing,X₂ between the scoring element 116 and the depth stop 138 of discpreparation instrument 100.

Vertebral endplates 338 a, 340 a are then scored with disc preparationinstrument 100. Scoring is effected by the rotation of T-handle 130which rotates scoring element 116 from the first position to the secondposition, as depicted in FIG. 14. Such rotation causes the abrasiveedges of first portion 116 a and second portion 116 b of scoring element116 to cut a slot 344 into endplates 338 a, 340 a. Complete penetrationof slots 344 into the bony/cartilaginous endplates 338 a, 340 a may notbe necessary as slots 344 provide a weakened, secured location tofacilitate entrance of anchor plates 240, 242 on cage implant 204.T-handle 130 may be actuated several times if necessary in order tosuitably form scored location 344, with proper penetration of scoringelement 116 being achieved when T-handle 130 is in a substantiallyvertical orientation. Upon achievement of endplate scoring, T-handle 130is rotated to the horizontal orientation to thereby rotate scoringelement 116 back to the first position wherein scoring element 116 liesfully contained within trial device 104. At this point in the procedure,trial device 104 is removed by manually pulling handle 120 in a proximaldirection.

As described hereinabove, trial body 106 of trial device 104 is of sizeand configuration approximating the size and configuration of cageimplant 204 for insertion into the disc space. As such, trial device 104may also be used to assess a space between two vertebrae. Thus, trialdevice 104 may serve two purposes—to prepare one or more endplatesurfaces for receiving cage implant 204 and to test a size for theselection of an appropriately sized cage implant 204. In this regard, aplurality of disc preparation instruments 100, each having a trialdevice 104 of different heights may be provided in a kit. Alternatively,a series of differently sized trial devices 104 may be provided in thekit for separate releasable attachment to a single elongate handle 102.In either case, a variety of trial devices 104 may be made available foruse in assessing the size of the disc space 342 for selection of anappropriately sized cage implant 204. A plurality of differently sizedcage implants 204 may be provided in the kit to allow for selectionbased upon the assessment of disc space 342.

Upon determination of the proper size of disc space 342 and selection ofan appropriately sized cage implant 204, the selected cage implant 204is releasably attached to elongate inserter 202 of inserter assembly200. Such attachment is effected by insertion of tips 260 of cageimplant support 256 into cage implant opening 216 until flexible hooks264 engage openings 230, 234 in sidewalls 210, 212, as described above.Pull rod 278 is then attached to anchor plate 208 by inserting distalend 278 a through deployment knob lumen 272 and through lumen 254 ofinserter grip 250 and inner sleeve 252 until threads 280 enter threadedopening 238 a of anchor plate 208. Pull rod knob 282 is rotated in aclockwise motion to thread pull rod threads 280 into threaded anchorplate opening 238 a. The measurement of depth stop 138, as observed andnoted on indicator device 158 of disc preparation tool 100, is thentransferred to inserter assembly 200. As such, where, for example, amarking 160 of indicator device 158 is observed through the “2” window,such reading is transferred to the “2” window of indicator device 336 ofinserter assembly 200. This establishes the distance, D, as describedhereinabove, that proximal surface 210 a, 212 a of cage implant 204 isspaced from shoulder 318 of inserter assembly 200. Having transferredthe depth reading, cage implant 204 is manipulated by inserter grip 250into the prepared disc space 342 until shoulder 318 contacts exterioranterior surface 338 c of vertebra 338. This then establishes thespacing, X₁ between anchor penetration tips 240 b, 242 b and shoulder318 of inserter assembly 200. At this point, anchor blade penetrationtips 240 b, 242 b are precisely aligned with slots 344 formed at thescored locations in respective vertebral endplates 338 a, 340 a, asshown in FIG. 15.

Having suitably positioned cage implant to 204 in disc space 342 andaligned anchor blade penetration tips 240 b, 242 b with slots 344,anchor blades 240, 242 are then deployed. Such deployment is effected,as described above, by clockwise rotation of deployment knob 270. Suchrotation of deployment knob 270 draws pull rod 278 in the proximaldirection, deploying anchor blades 240 and 242 to the deployed secondposition, such that anchor blade penetration tips 240 b, 242 b penetrateinto vertebral bodies 338 b, 340 b through scored locations 344, asshown in FIG. 16. After completion of the deployment of anchor blades240, 242, elongate inserter 202 is separated from cage implant 204 byproximal movement of hook actuator 314, as explained above. With cageimplant 204 suitably inserted in disc space 342, and anchor blades 240,242 properly deployed, bone graft or other suitable fusion promotionmaterials may be introduced into opening 216 of cage implant 204 andaround anchor plate 208. A cap 346, as shown in FIG. 17 may be attachedto the proximal end of cage implant 204 so as to provide a barrier tomaintain bone graft material in place within cage implant opening 216.Attachment of cap 346 to cage implant 204 may be effected by using cageimplant windows 230, 234 and or channel 232, 236 as attachment surfaces.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same should be considered asillustrative and not restrictive in character. It is understood thatonly the preferred embodiments have been presented and that all changes,modifications and further applications that come within the spirit ofthe invention are desired to be protected.

What is claimed is:
 1. A method for fusing together a superior vertebraand an inferior vertebra, the superior vertebra including an inferiorendplate and a vertebral body, said vertebral body of said superiorvertebra having an exterior surface, the inferior vertebra including asuperior endplate and a vertebral body, said vertebral body of saidinferior vertebra having an exterior surface, the superior and inferiorendplates defining a disc space therebetween, the method comprising thesteps of: introducing into said disc space a trial device supported by afirst instrument, said first instrument comprising an adjustable depthstop movable with respect to a first location on said trial device by aselectively adjustable first distance, said first instrument includingan indicator device having indicia changeable with and correlated tosaid first distance; moving said depth stop on said first instrumentuntil said depth stop contacts the exterior surface of one of saidsuperior or inferior vertebrae, thereby establishing a selected firstdistance; noting an indicia displayed by said indicator device, suchindicia being indicative of said selected first distance; providing asecond instrument supporting a cage implant, said second instrumentcomprising an adjustable shoulder serving as a depth stop, said shoulderbeing movable with respect to a second location on said cage implant bya selectively adjustable second distance correlated with saidselectively adjustable first distance, said second instrument includingan indicator device having indicia changeable with and correlated tosaid second distance, such that a display of the same indicia on saidfirst instrument and said second instrument indicates that said firstdistance and said second distance are substantially equal; moving saidshoulder on said second instrument until said indicia on said secondinstrument indicates the same indicia as the indicia noted on said firstinstrument; and inserting said cage implant into said disc space untilsaid shoulder contacts the exterior surface of one of said superior orinferior vertebrae, thereby establishing that the depth of said secondlocation within said disc space from the exterior surface of said one ofsaid first or second vertebrae is substantially the same as saidselected first distance.
 2. The method of claim 1, wherein said firstinstrument comprises an elongate handle supporting said trial device,said adjustable stop being movable axially on said handle, said trialdevice being of size and configuration approximating the size andconfiguration of a cage implant for insertion into said disc space, saidtrial device having a distal surface, a proximal surface, a top surfaceand a bottom surface.
 3. The method of claim 2, wherein said firstlocation is said proximal surface of said trial device.
 4. The method ofclaim 1, wherein said trial device comprises a scoring elementselectively movable from a first position to a second position forscoring an inferior endplate of said superior vertebra or for scoring asuperior endplate of said inferior vertebra, and wherein said methodincludes the step of scoring one of said superior or inferior endplateswith said scoring element.
 5. The method of claim 4, wherein said firstlocation is said scoring element.
 6. The method of claim 1, wherein saidsecond instrument comprises an inserter supporting said cage implant,said cage implant comprising a cage of size and configuration forinsertion into said disc space, said cage having a distal surface, aproximal surface, a top surface and a bottom surface, wherein saidmethod includes the step of inserting said cage implant into said discspace with said inserter.
 7. The method of claim 6, wherein said secondlocation is said proximal surface of said cage.